In recent years, in the field of the surface packaging of electronic parts, the packaging of leaded parts, such as QFP or SOP, has been practiced with increasing frequency, and to ensure satisfactory packaging of these parts without positional deviation during mounting, it has become necessary to identify the position of the leads of the parts. Particularly, the identification of the position of the front ends of the leads is a very important factor in positioning the parts or knowing the parts shape during packaging.
A conventional parts identifying device will now be described using FIGS. 6, 7 and 8. A description only of the parts identifying process using an identifying system will be given herein, while leaving out a description of the process for packaging electronic parts.
In FIG. 6, the numeral 101 denotes an electronic part depicted in image data to be processed for identification by an identifying system in an electronic parts packaging plant. The electronic part 101 is equipped with a plurality of leads 102 on an optional side or sides thereof. The leads 102 are disposed in parallel on a side or sides of the electronic part 101.
The parts identifying process using a conventional parts identifying device will now be described.
First, at the step #11 of a flowchart shown in FIG. 8, a test window 103 shown in FIGS. 6 and 7 is defined. The test window 103 is used to define the range for processing the image data on the whole or part of the electronic part obtained by a pickup tube used when identifying parts. The X-direction of the test window 103 is determined by one method or another such that it is parallel with the direction in which the leads 102 are juxtaposed. Such method will not be described herein.
At the step #12 of the flowchart shown in FIG. 8, the values of light intensity in the X-direction within the test window are added for each Y-coordinate to provide histogram data 104 to be used in the identification process.
This process is intended to detect the position of the leads 101 in the lengthwise direction, i.e., the Y-direction of the test window 103 and calculate the front end position of the leads 102; therefore, even with the histogram data 104 produced in the aforesaid process, the detection of the front end position of the leads 102 is possible. The histogram data 104 for effecting said process is produced in the manner shown in FIG. 7.
Finally, at the step #13 of the flowchart shown in FIG. 8, a differential process is performed on the histogram data 104 to produce differential data 105 shown in FIG. 7. This process is a process for calculating the position at which the rate of change of light intensity in the histogram data 104 is at the maximum. In the differential data 105, this position corresponds to the peak point 106 where the differential value is at the maximum. Thus, the position of the peak point 106 corresponds to the Y-direction position of the leads 102 in the test window 103. Thus, the front end position of the leads 102 present in the test window 103 is calculated from data on the relative position between the test window 103 and the reference position of the electronic part 101 with respect to the nozzle center or the like.
In the case where the leads 102 are present on a plurality of sides of the electronic part 101, said processing is performed for each of the test windows associated with the plurality of sides, whereby the front end position of the electronic parts can be identified and so can be the shape of the electronic part 101.
However, in the parts identifying process using said conventional parts identifying device described above, if there is a noise 107 in the test window 103, as shown in FIG. 9, there are produced histogram data 108 and differential data 109 as shown in this figure. Since the differential date 109 has a plurality of peak points, such as shown at a, b and c, there has been a problem that despite the fact that the actual front end position of the leads is the position corresponding to the peak point a of the differential data 109, the position corresponding to the peak point b or c would be erroneously identified as the front end position of the leads, depending upon the method for peak point detection employed.